Rubber composition, laminated body of rubber composition and metal, and vulcanized rubber product

ABSTRACT

A rubber composition of the present technology comprises: from 0.5 parts by mass to 1.5 parts by mass of sulfur, from 0.2 parts by mass to 0.6 parts by mass of a thiuram vulcanization accelerator, from 0.2 parts by mass to 0.6 parts by mass of a guanidine vulcanization accelerator, from 0.15 parts by mass to 0.8 parts by mass of a sulfenamide vulcanization accelerator, and from 0.1 parts by mass to 1.5 parts by mass of a thiourea vulcanization accelerator per 100 parts by mass of a diene polymer containing a chloroprene rubber.

RELATED APPLICATIONS

This application is a divisional of U.S. patent application Ser. No.14/409,800, filed on Dec. 19, 2014, which is the National Stage ofInternational Patent Application No. PCT/JP2014/063231, filed on May 19,2014.

TECHNICAL FIELD

The present technology relates to a rubber composition, a laminated bodyof the rubber composition and a metal, and a vulcanized rubber product,and particularly relates to a rubber composition, a laminated body ofthe rubber composition and a metal, and a vulcanized rubber productcontaining a plurality of vulcanization accelerator.

BACKGROUND

Conventionally, chloroprene rubber compositions for manufacturinghydraulic hose and high pressure hose in which a reinforcing layerhaving a surface plated with a metal such as brass is sandwiched by apair of rubber layers have been proposed (e.g. see Japanese UnexaminedPatent Application Publication No. 2001-279022A). Since this rubbercomposition contains a vulcanization accelerator such as sulfurs andguanidines, crosslinking characteristics of a rubber layer formed fromthe rubber composition is enhanced, and adhesion between a metal surfaceof the reinforcing layer and the rubber layer is enhanced.

Methods of manufacturing hose described above include a steamvulcanization method in which the rubber composition is heated andvulcanized by steam, and an oven vulcanization method in which therubber composition is heated and vulcanized by an oven. Since the ovenvulcanization method allows continuous vulcanization, productivity ofhose can be enhanced.

However, when vulcanization of a rubber composition is performed by theoven vulcanization method, sufficient adhesion between the rubber layerand the reinforcing layer may not be always obtained due to vaporizationof remarkable amount of water during the vulcanization. Therefore, therehas been a demand for a rubber composition that has excellent heatresistance and that can provide a rubber layer having excellent adhesiontoward a reinforcing layer even when vulcanized by a hot-airvulcanization method such as the oven vulcanization method.

SUMMARY

The present technology provides a rubber composition that has excellentheat resistance and that can provide a rubber layer having excellentadhesion toward a reinforcing layer even when the rubber composition isvulcanized by a hot-air vulcanization method, a laminated body of therubber composition and a metal, and a vulcanized rubber product.

A rubber composition of the present technology comprises: from 0.5 partsby mass to 1.5 parts by mass of sulfur, from 0.2 parts by mass to 0.6parts by mass of a thiuram vulcanization accelerator, from 0.2 parts bymass to 0.6 parts by mass of a guanidine vulcanization accelerator, from0.15 parts by mass to 0.8 parts by mass of a sulfenamide vulcanizationaccelerator, and from 0.1 parts by mass to 1.5 parts by mass of athiourea vulcanization accelerator per 100 parts by mass of a dienepolymer containing a chloroprene rubber.

In the rubber composition of the present technology, a content of thechloroprene rubber in the diene polymer is preferably from 40 mass % to100 mass %, and a content of a styrene butadiene rubber in the dienepolymer is preferably from 0 mass % to 60 mass %.

A laminated body of a rubber composition and a metal of the presenttechnology comprises: a rubber layer containing the rubber compositiondescribed in claim 1 or 2; and a reinforcing layer that is provided onthe rubber layer and has a metal surface.

In the laminated body of a rubber composition and a metal of the presenttechnology, the metal surface is preferably formed by plating withbrass.

In the laminated body of a rubber composition and a metal of the presenttechnology, the reinforcing layer preferably has a braided structure inwhich wires have been braided, or a spiral structure.

A vulcanized rubber product of the present technology is obtained byusing the rubber composition described above.

In the vulcanized rubber product of the present technology, the rubberlayer of the laminated body of a rubber composition and a metaldescribed above is vulcanized in the presence of sulfur and adhered tothe reinforcing layer.

The vulcanized rubber product of the present technology is preferably ahose.

The hose of the present technology is produced by vulcanizing in an ovenvulcanization device.

According to the present technology, a rubber composition that hasexcellent heat resistance and that can provide a rubber layer havingexcellent adhesion toward a reinforcing layer even when the rubbercomposition is vulcanized by a hot-air vulcanization method, a laminatedbody of the rubber composition and a metal, and a vulcanized rubberproduct can be produced.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic perspective view of an example of a hydraulic hoseaccording to an embodiment of the present technology.

FIG. 2 is an explanatory diagram of production steps of a hydraulic hoseusing a rubber composition according to an embodiment of the presenttechnology.

FIG. 3 is an explanatory diagram of vulcanization steps of the hydraulichose using the rubber composition according to the embodiment of thepresent technology.

FIG. 4 is a partially cross-sectional view illustrating an example of alayer structure around a mandrel inserted into a vulcanization device ofproduction steps of a hydraulic hose using a rubber compositionaccording to an embodiment of the present technology.

DETAILED DESCRIPTION

An embodiment of the present technology will be described below indetail with reference to the attached drawings. Note that the presenttechnology is not limited to the embodiment described below and can beperformed with suitable modifications.

A rubber composition according to the present embodiment comprises: from0.5 parts by mass to 1.5 parts by mass of sulfur, from 0.2 parts by massto 0.6 parts by mass of a thiuram vulcanization accelerator, from 0.2parts by mass to 0.6 parts by mass of a guanidine vulcanizationaccelerator, from 0.15 parts by mass to 0.8 parts by mass of asulfenamide vulcanization accelerator, and from 0.1 parts by mass to 1.5parts by mass of a thiourea vulcanization accelerator per 100 parts bymass of a diene polymer containing a chloroprene rubber.

Since the rubber composition according to the present embodimentcontains a predetermined amount of sulfur and four types ofvulcanization accelerators including the thiuram vulcanizationaccelerator, guanidine vulcanization accelerator, sulfenamidevulcanization accelerator, and thiourea vulcanization acceleratorrelative to the amount of the diene rubber polymer, vulcanizationproperties are enhanced in a well-balanced manner due to the synergisticeffect of vulcanization accelerators. Because of this, adhesion betweena rubber layer and a reinforcing layer is enhanced even when the rubberlayer is formed by the rubber composition provided on the reinforcinglayer having a metal surface formed by plating with brass and thenoven-vulcanized.

<Diene Polymer>

As the diene polymer, a diene polymer containing a chloroprene rubber(CR) is used. “Chloroprene rubber (CR)” refers to a homopolymer ofchloroprene monomers (hereinafter referred to as chloroprene-basedmonomer) or a copolymer obtained by polymerizing a chloroprene monomerand a mixture of at least one type of another monomer that can becopolymerized with the chloroprene monomer (hereinafter referred to aschloroprene-based polymer).

Chloroprene rubbers are classified into a sulfur-modified type, amercaptan-modified type, and a xanthogen-modified type depending on thetypes of the molecular weight modifier. As the chloroprene rubber, anyof the modified-types can be used. Among these, since themercaptan-modified type and the xanthogen-modified type lead toexcellent heat resistance of the polymer itself compared to thesulfur-modified type, the mercaptan-modified type and thexanthogen-modified type are preferable for cases where higher heatresistance is required.

The sulfur-modified type chloroprene rubber is a chloroprene rubberobtained by plasticizing, with thiuram disulfide, a polymer obtained bycopolymerizing sulfur and chloroprene monomers or chloroprene-basedmonomers, and then adjusting to have a predetermined Mooney viscosity.

The mercaptan-modified type chloroprene rubber is a chloroprene rubberobtained by using an alkylmercaptan such as n-dodecyl mercaptan,tert-dodecyl mercaptan, and octyl mercaptan as a molecular weightmodifier.

The xanthogen-modified type chloroprene rubber is a chloroprene rubberobtained by using an alkyl xanthogen compound as a molecular weightmodifier. The alkyl xanthogen compound is not particularly limited andcan be selected appropriately depending on the purpose. Examples of thealkyl xanthogen compound include dimethylxanthogen disulfide,diethylxanthogen disulfide, diisopropylxanthogen disulfide,diisobutylxanthogen disulfide, and the like.

The used amount of the alkyl xanthogen compound is not particularlylimited as long as the used amount is selected in the manner that themolecular weight (or the Mooney viscosity) of the chloroprene rubberbecomes appropriate, and the used amount can be selected appropriatelydepending on the purpose (structure of the alkyl group or targetedmolecular weight). The used amount of the alkyl xanthogen compound ispreferably from 0.05 parts by mass to 5.0 parts by mass, and morepreferably from 0.3 parts by mass to 1.0 parts by mass per 100 parts bymass of chloroprene monomers or chloroprene-based monomers.

As the diene polymer, another diene polymer that is sulfur vulcanizableexcept chloroprene rubber in a range that the effect of the presenttechnology can be exhibited. Here, “sulfur vulcanizable” means having aproperty that can form a crosslinking structure via sulfur. Examples ofthe another diene polymer include a natural rubber (NR), isoprene rubber(IR), styrene butadiene rubber (SBR), acrylonitrile-butadiene rubber(NBR), and ethylene-propylene-diene rubber (EPDM). By using these,various physical properties that are required for a rubber compositionfor hose can be exhibited at a high level. One type of these dienepolymers may be used alone, or two or more types of these diene polymersmay be used in a combination.

In the present embodiment, a diene polymer having a content of thechloroprene rubber (CR) of 40 mass % to 100 mass %, and a content of astyrene butadiene rubber (SBR) of 0 mass % to 60 mass % is preferablyused from the perspectives of heat resistance of the rubber compositionand adhesion of the rubber composition to the metal surface of thereinforcing layer.

The compounded amount of the diene polymer is preferably from 20 mass %to 70 mass % relative to the total amount of the rubber composition fromthe perspectives of imparting good mixing processability and goodappearance to the rubber.

<Vulcanizing Agent>

The rubber composition according to the present embodiment containssulfur as the vulcanizing agent. Examples of sulfur include powderedsulfur, precipitated sulfur, highly dispersible sulfur, surface treatedsulfur, and insoluble sulfur.

The content of sulfur is from 0.5 parts by mass to 1.5 parts by mass per100 parts by mass of the diene polymer. If the content of sulfur is from0.5 parts by mass to 1.5 parts by mass, a rubber composition havingexcellent heat resistance as well as excellent adhesion between a rubberlayer using the rubber composition and the reinforcing layer can beobtained. The content of sulfur is preferably 0.55 parts by mass orgreater, more preferably 0.6 parts by mass or greater, furtherpreferably 0.7 parts by mass or greater, and yet further preferably 0.8parts by mass or greater, and preferably 1.3 parts by mass or less, morepreferably 1.2 parts by mass or less, further preferably 1.1 parts bymass or less, and yet further preferably 1.0 parts by mass or less, per100 parts by mass of the diene polymer. Taking these into consideration,the content of sulfur is preferably from 0.55 parts by mass to 1.3 partsby mass, more preferably from 0.6 parts by mass to 1.2 parts by mass,further preferably from 0.7 parts by mass to 1.1 parts by mass, and yetfurther preferably from 0.8 parts by mass to 1.0 parts by mass, per 100parts by mass of the diene polymer.

The rubber composition according to the present embodiment may containanother vulcanizing agent other than sulfur in a range that the effectof the present technology can be exhibited. Examples of the vulcanizingagent other than sulfur include sulfur-based, organic peroxide-based,metal oxide-based, phenolic resin, quinone dioxime, and the like. Onetype of these vulcanizing agents other than sulfur may be used alone, ortwo or more types of these vulcanizing agents other than sulfur may beused in a combination. Examples of the sulfur-based vulcanizing agentinclude, but except the thiuram vulcanization accelerator used in therubber composition according to the present technology, organicsulfur-containing compounds such as dimorpholine disulfide andalkylphenol disulfide.

Examples of the organic peroxide-based vulcanizing agent include dicumylperoxide, benzoyl peroxide, t-butyl hydroperoxide, 2,4-dichlorobenzoylperoxide, 2,5-dimethyl-2,5-di(t-butylperoxy)hexane, and2,5-dimethylhexane-2,5-di(peroxyl benzoate).

Examples of the other vulcanizing agent include zinc oxide, magnesiumoxide, resins such as phenol resin, p-quinone dioxime,p-dibenzoylquinone dioxime, poly-p-dinitrosobenzene, methylenedianiline,and the like.

<Vulcanization Accelerator>

The rubber composition according to the present embodiment contains athiuram vulcanization accelerator, guanidine vulcanization accelerator,sulfenamide vulcanization accelerator, and thiourea vulcanizationaccelerator. In the rubber composition according to the presentembodiment, by using sulfur as the vulcanizing agent described above,and four types of vulcanization accelerators including the thiuramvulcanization accelerator, guanidine vulcanization accelerator,sulfenamide vulcanization accelerator, and thiourea vulcanizationaccelerator, heat resistance of the rubber composition and adhesionbetween a rubber layer using the rubber composition and a metal surfaceof a reinforcing layer can be enhanced.

The content of the thiuram vulcanization accelerator is from 0.2 partsby mass to 0.6 parts by mass per 100 parts by mass of the diene polymer.If the content of the thiuram vulcanization accelerator is from 0.2parts by mass to 0.6 parts by mass, a rubber composition havingexcellent heat resistance as well as excellent vulcanizationcharacteristics and excellent adhesion between a rubber layer using therubber composition and the reinforcing layer can be obtained. Examplesof the thiuram vulcanization accelerator include dipentamethylenethiuramtetrasulfide, tetramethylthiuram monosulfide (TS), tetramethylthiuramdisulfide (TT), tetraethylthiuram disulfide (TETD), tetrabutylthiuramdisulfide (TBTD), tetrabenzylthiuram disulfide,tetrakis(2-ethylhexyl)thiuram disulfide, and the like.

The content of the thiuram vulcanization accelerator is preferably 0.25parts by mass or greater, more preferably 0.3 parts by mass or greater,further preferably 0.35 parts by mass or greater, and preferably 0.55parts by mass or less, more preferably 0.50 parts by mass or less,further preferably 0.45 parts by mass or less, per 100 parts by mass ofthe diene polymer. The content of the thiuram vulcanization acceleratoris preferably from 0.25 parts by mass to 0.55 parts by mass, morepreferably from 0.3 parts by mass to 0.5 parts by mass, and furtherpreferably from 0.35 parts by mass to 0.45 parts by mass, per 100 partsby mass of the diene polymer.

The content of the guanidine vulcanization accelerator is from 0.2 partsby mass to 0.6 parts by mass per 100 parts by mass of the diene polymer.If the content of the guanidine vulcanization accelerator is from 0.2parts by mass to 0.6 parts by mass, a rubber composition havingexcellent heat resistance as well as excellent vulcanizationcharacteristics and excellent adhesion between a rubber layer using therubber composition and the reinforcing layer can be obtained. Examplesof the guanidine vulcanization accelerator includeN,N′-diphenylguanidine, N,N′-di-ortho-tolylguanidine, and the like.

The content of the guanidine vulcanization accelerator is preferably0.25 parts by mass or greater, more preferably 0.3 parts by mass orgreater, further preferably 0.35 parts by mass or greater, andpreferably 0.55 parts by mass or less, more preferably 0.50 parts bymass or less, further preferably 0.45 parts by mass or less, per 100parts by mass of the diene polymer from the perspectives of obtaining arubber composition having excellent heat resistance as well as excellentadhesion between a rubber layer using the rubber composition and thereinforcing layer. The content of the guanidine vulcanizationaccelerator is preferably from 0.25 parts by mass to 0.55 parts by mass,more preferably from 0.3 parts by mass to 0.5 parts by mass, and furtherpreferably from 0.35 parts by mass to 0.45 parts by mass, per 100 partsby mass of the diene polymer.

The content of the sulfenamide vulcanization accelerator is from 0.15parts by mass to 0.8 parts by mass per 100 parts by mass of the dienepolymer. If the content of the sulfenamide vulcanization accelerator isfrom 0.15 parts by mass to 0.8 parts by mass, a rubber compositionhaving excellent heat resistance as well as excellent vulcanizationcharacteristics and excellent adhesion between a rubber layer using therubber composition and the reinforcing layer can be obtained. Examplesof the sulfenamide vulcanization accelerator includeN-cyclohexyl-2-benzothiazolyl sulfenamide (CZ),N-t-butyl-2-benzothiazolyl sulfenamide (NS),N-oxydiethylene-2-benzothiazolyl sulfenamide,N,N-diisopropyl-2-benzothiazolyl sulfenamide,N,N-dicyclohexyl-2-benzothiazolyl sulfenamide, and the like.

The content of the sulfenamide vulcanization accelerator is preferably0.2 parts by mass or greater, more preferably 0.25 parts by mass orgreater, further preferably 0.3 parts by mass or greater, and preferably0.75 parts by mass or less, more preferably 0.7 parts by mass or less,further preferably 0.65 parts by mass or less, per 100 parts by mass ofthe diene polymer from the perspectives of obtaining a rubbercomposition having excellent heat resistance as well as excellentadhesion between a rubber layer using the rubber composition and thereinforcing layer. The content of the sulfenamide vulcanizationaccelerator is preferably from 0.2 parts by mass to 0.75 parts by mass,more preferably from 0.25 parts by mass to 0.7 parts by mass, andfurther preferably from 0.3 parts by mass to 0.65 parts by mass, per 100parts by mass of the diene polymer.

The content of the thiourea vulcanization accelerator is from 0.1 partsby mass to 1.5 parts by mass per 100 parts by mass of the diene polymer.If the content of the thiourea vulcanization accelerator is from 0.1parts by mass to 1.5 parts by mass, a rubber composition havingexcellent heat resistance as well as excellent adhesion between a rubberlayer using the rubber composition and the reinforcing layer can beobtained.

The content of the thiourea vulcanization accelerator is preferably 0.2parts by mass or greater, more preferably 0.3 parts by mass or greater,further preferably 0.4 parts by mass or greater, and preferably 1.3parts by mass or less, more preferably 1.2 parts by mass or less,further preferably 1.1 parts by mass or less, per 100 parts by mass ofthe diene polymer from the perspectives of obtaining a rubbercomposition having excellent heat resistance as well as excellentadhesion between a rubber layer using the rubber composition and thereinforcing layer. The content of the thiourea vulcanization acceleratoris preferably from 0.2 parts by mass to 1.3 parts by mass, morepreferably from 0.3 parts by mass to 1.2 parts by mass, and furtherpreferably from 0.4 parts by mass to 1.1 parts by mass, per 100 parts bymass of the diene polymer. Examples of the thiourea vulcanizationaccelerator include ethylene thiourea(2-mercaptoimidazoline),N,N′-diethyl thiourea, trimethyl thiourea, N,N′-dibutyl thiourea, andthe like.

The rubber composition according to the present embodiment may containanother vulcanizing agent other than the vulcanizing agent describedabove in a range that the effect of the present technology can beexhibited. Examples of another vulcanization accelerator includealdehyde-ammonia vulcanization accelerator, aldehyde-amine vulcanizationaccelerator, thiazole vulcanization accelerator, dithiocarbamatevulcanization accelerator, xanthogenate vulcanization accelerator, andthe like. One type of these may be used alone, or two or more types ofthese may be used in a combination.

[Other Additives]

The rubber composition may contain other additives, if necessary, in arange that the effect of the present technology can be exhibited.Examples of the other additive include fillers, plasticizers, softeners,antiaging agents, organic activators, antioxidants, antistatic agents,flame retardants, crosslinking-accelerating auxiliaries, vulcanizationretarders, antiozonants, aroma oil, adhesive auxiliaries, and the like.

Examples of the fillers include carbon black, silica (white carbonblack), clay, talc, iron oxide, zinc oxide (ZnO), titanium oxide, bariumoxide, magnesium oxide, calcium carbonate, magnesium carbonate, zinccarbonate, barium sulfate, mica, diatomaceous earth, and the like. Onetype of these fillers may be used alone, or two or more types of thesefillers may be used in a combination. As the carbon black, any carbonblack can be suitably selected and used depending on the purpose. ISAFgrade and FEF grade carbon blacks are preferable. Examples of the silicainclude crystallized silica, amorphous silica (e.g. high temperaturetreated silica), fumed silica, calcined silica, precipitated silica,pulverized silica, molten silica, and the like. In particular, silica isknown to generate a carbon gel (bound rubber) in the similar manner asin carbon black and can be suitably used if necessary. Examples of theclay include hard clay, pyropyllite clay, kaolin clay, calcined clay,and the like.

Examples of the plasticizer include dioctyl phthalate (DOP), dibutylphthalate (DBP), dioctyl adipate (DOA), isodecyl succinate, di(ethyleneglycol) dibenzoate, pentaerythritol ester, butyl oleate, methyl acetylricinoleate, tricresyl phosphate, trioctyl phosphate, trimellitic acidester, propylene glycol adipate polyester, butylene glycol adipatepolyester, naphthenic oil, and the like. One type of these plasticizersmay be used alone, or two or more types of these plasticizers may beused in a combination.

Specific examples of the softener include aromatic oil, naphthenic oil,paraffinic oil, petroleum resin, vegetable oil, liquid rubber, and thelike. One type of these softeners may be used alone, or two or moretypes of these softeners may be used in a combination.

Examples of the antiaging agent includeN-(1,3-dimethylbutyl)-N′-phenyl-p-phenylenediamine (6PPD),N,N′-dinaphthyl-p-phenylenediamine (DNPD),N-isopropyl-N′-phenyl-p-phenylenediamine (IPPD), styrenated phenol (SP),2,2,4-trimethyl-1,2-dihydroquinoline polymer (RD), and the like. Onetype of these antiaging agents may be used alone, or two or more typesof these antiaging agents may be used in a combination.

Examples of the organic activator include stearic acid, oleic acid,lauric acid, zinc stearate, and the like. One type of these organicactivators may be used alone, or two or more types of these organicactivators may be used in a combination.

Examples of the antioxidant include butylhydroxytoluene (BHT) andbutylhydroxyanisole (BHA).

Examples of the antistatic agent include quaternary ammonium salts; andhydrophilic compounds such as polyglycols and ethylene oxidederivatives.

Examples of the flame retardant include chloroalkyl phosphates,dimethyl-methyl phosphonates, bromine-phosphorus compounds, ammoniumpolyphosphates, neopentyl bromide polyethers, brominated polyethers, andthe like. Examples of non-halogen-based flame retardant include aluminumhydroxide, magnesium hydroxide, tricresyl phosphate, and diphenyl cresylphosphate.

A conventional auxiliary for rubber can be used together as acrosslinking-accelerating auxiliary. As the auxiliary for rubber, zincoxide, magnesium oxide; stearic acid, oleic acid, and Zn salts of thesecan be used.

Examples of the vulcanization retarder include organic acids such asphthalic anhydride, benzoic acid, salicylic acid, and acetylsalicylicacid; nitroso compounds such as polymers of N-nitroso-diphenylamine,N-nitroso-phenyl-β-naphthylamine, andN-nitroso-trimethyl-dihydroquinoline; halides such as trichloromelanine;2-mercaptobenzimidazole, N-(cyclohexylthio)phthalimide (PVI), and thelike. One type of these vulcanization retarders may be used alone, ortwo or more types of these vulcanization retarders may be used in acombination.

Examples of the adhesive auxiliary include triazine thiol compounds(e.g. 2,4,6-trimercapto-1,3,5-triazine and6-butylamino-2,4-dimercapto-1,3,5-triazine), resorcin, cresol,resorcin-formalin latex, monomethylol melamine, monomethylol urea,ethylene maleimide, cobalt naphthenate, cobalt stearate, cobaltversatate, cobalt dodecanoate, and the like. One type of these adhesiveauxiliaries may be used alone, or two or more types of these adhesiveauxiliaries may be used in a combination.

<Method of Producing Rubber Composition>

The rubber composition according to the present embodiment can beproduced by a conventionally known production method. An example of themethod of producing the rubber composition according to the presentembodiment is a production method comprising the steps of: compoundingthe diene polymer described above, and as necessary, another dienepolymer, a polymer other than the diene polymer, and various additivesdescribed above; and kneading the mixture using an internal mixer suchas a Banbury mixer or a kneader, a roll kneader such as a roll, anextruder, a twin screw extruder, or the like.

[Laminated Body of the Rubber Composition and a Metal]

The laminated body of the rubber composition and a metal according tothe present embodiment is a laminated body of the rubber compositiondescribed above and a reinforcing layer of a wire having a metal platedsurface. Examples of this laminated body include a high pressure hose,hydraulic hose, and the like. FIG. 1 is a partial cutaway perspectiveview of an example of a hydraulic hose according to the presentembodiment. As illustrated in FIG. 1, the hydraulic hose 1 is formedcylindrically and comprises an inner rubber layer 11 for passing fluidtherein, a reinforcing layer 12 provided on the outer side of the innerrubber layer 11, and an outer rubber layer 13 provided on the outer sideof the reinforcing layer 12. The reinforcing layer 12 is arranged in themanner that the inner rubber layer 11 and the outer rubber layer 13sandwich the reinforcing layer 12. The inner rubber layer 11, thereinforcing layer 12, and the outer rubber layer 13 are adhered andfixed due to the vulcanization of the inner rubber layer 11 and theouter rubber layer 13.

<Rubber Layer>

As described above, the inner rubber layer 11 and/or the outer rubberlayer 13 are rubber layers in which the rubber composition according tothe present embodiment is used. From the perspective of weatherabilityof the hose, it is preferable to form at least the outer rubber layer 13using the rubber composition according to the present embodiment. Theinner rubber layer 11 is preferably formed by using a rubber compositioncontaining an acrylonitrile butadiene rubber (NBR) having excellent oilresistance as a main component.

The thickness of the inner rubber layer 11 is, for example, preferablyfrom 0.2 mm to 4.0 mm, and more preferably from 0.5 mm to 2.0 mm.Similarly, the thickness of the outer rubber layer 13 is, for example,preferably from 0.2 mm to 4.0 mm, and more preferably from 0.5 mm to 2.0mm.

<Reinforcing Layer>

The reinforcing layer 12 is a wire braid in which steel wires having asurface plated with brass are braided. From the perspective ofmaintaining the strength of the hydraulic hose 1, the reinforcing layer12 is a layer provided in between the inner rubber layer 11 and theouter rubber layer 13. Note that, in the example illustrated in FIG. 1,the reinforcing layer 12 is one layer; however, a plurality of thereinforcing layers 12 in which middle rubber layer(s) is(are) providedin between the layers may be provided. The reinforcing layer 12 may be,other than a wire braid, spiral wires formed by winding steel wiresspirally around the inner rubber layer 11. Materials, and a braidingmethod, weaving method, or winding method that forms the reinforcinglayer 12 can be suitably selected depending on the application, forexample depending on pressure resistance. In the hydraulic hose and thelike, the reinforcing layer 12 is preferably formed by a wire braid.

Examples of the wire materials include piano wires (carbon steel), hardsteel wires, and stainless steel wires. From the perspectives ofprocessability and strength, piano wires (carbon-steel) and hard steelwires are particularly preferable as the wire materials.

In order to enhance the adhesion toward the rubber layer, the surface ofthe reinforcing layer 12 is plated with a metal. This metal plating is abrass coating applied on piano wires and hard steel wires. The brasscoating is formed by plating a steel wire with copper, plating with zincover the copper, and then subjecting the wire to thermal diffusionprocessing.

<Vulcanized Rubber Product>

In the laminated body of the rubber composition and a metal of therubber composition and the reinforcing layer 12 described above,molecules in the rubber forming the inner rubber layer 11 and the outerrubber layer 13 are crosslinked each other by sulfur when crosslinked,i.e. vulcanized, in the presence of sulfur. This crosslinking impartselasticity and tensile strength to the inner rubber layer 11 and theouter rubber layer 13, and adheres the inner rubber layer 11 and theouter rubber layer 13 to the reinforcing layer 12 due to the bond formedbetween the sulfur and the metal (copper, zinc) constituting the brasscoating, at the interface between the rubber layers and the reinforcinglayer 12.

Sulfur is preferably blended together with other materials when acompound of the rubber composition is formed. Note that the time atwhich sulfur is blended is not limited to the time when the compound isprepared as long as molecules forming the diene polymer are crosslinkedeach other by the sulfur, and as long as the inner rubber layer 11 andthe outer rubber layer 13 are adhered to the reinforcing layer 12 due tothe bond formed between the sulfur and the metal (copper, zinc) at theinterface between the inner rubber layer 11 and the outer rubber layer13 and the reinforcing layer 12, and the like.

An example of the method of vulcanization is a method in which therubber composition is heat treated at a predetermined temperature forpredetermined time period in the presence of sulfur. The vulcanizationtemperature is preferably from 130° C. to 180° C. The vulcanization timeis preferably from 30 minutes to 240 minutes. By a combination of thetemperature and the time in these ranges, desired physical properties asa vulcanized rubber product such as elasticity, tensile strength,appearance, adhesion at the interface between the rubber and the metal,and rubber adhesion at the interface between the rubber and the metalcan be imparted.

The vulcanized rubber product in the present embodiment can be suitablyused as hydraulic hose and the like. Examples of the method of producinghydraulic hose and the like include a steam vulcanization method inwhich the laminated body of the rubber composition and a metal is placedand sealed in a pressure vessel and crosslinked in a steam boiler, andan oven vulcanization method in which the laminated body of the rubbercomposition and a metal is covered with a nylon cloth or the like andvulcanized in a hot-air drying oven. In general, the steam vulcanizationmethod is a batch type treatment, and the oven vulcanization method is acontinuous type treatment. The method of producing hydraulic hose ispreferably an oven vulcanization method which is a continuous typetreatment.

<Method of Producing Vulcanized Rubber Product>

A method of producing vulcanized rubber product according to the presentembodiment will be described below. Here, an example of the case where ahydraulic hose is produced as the vulcanized rubber product will bedescribed.

The method of producing a hydraulic hose according to the presentembodiment will be described with reference to FIGS. 2 and 3. FIG. 2 isan explanatory diagram of production steps of a hydraulic hose using arubber composition according to an embodiment of the present technology.FIG. 3 is an explanatory diagram of vulcanization steps of the hydraulichose using the rubber composition according to the embodiment of thepresent technology.

<Steps of Producing Hose>

As illustrated in FIG. 2, the rubber hose is obtained by an extrusionstep of a rubber material that forms the inner rubber layer 11 (stepS101), a braiding step of the reinforcing layer 12 (step S102), anextrusion-vulcanization step of the outer rubber layer 13 (step S103),and a removing step of mandrel 101 (step S104). The produced rubber hoseis subjected to a water pressure test and a winding test step, and thenpackaged and shipped.

In the step S101, the outer circumferential surface of a mandrel 101that is sent out from an unwinding machine 100 is covered by anunvulcanized inner rubber layer 11 via a first extruder 102. A hose 103which is covered by the inner rubber layer 11 is wound by awinding-unwinding machine 104.

Next, in the step S102, a reinforcing layer 12 is braided by a braidingmachine 105 in the manner that the inner rubber layer 11 constitutingthe hose 103 sent out from the winding-unwinding machine 104 is covered,to form a hose 106, and then the hose 106 is wound by thewinding-unwinding machine 107. A metal wire is used as the code of thisreinforcing layer 12. As the metal wire, a steel wire plated with brassis used in order to impart excellent adhesion toward rubber. Note thatthe reinforcing layer 12 may be formed by spirally winding the metalwire around the inner rubber layer 11 that is formed around the mandrel101.

Next, in the step S103, a hose body 109 is formed by covering thereinforcing layer 12 of the hose 106 sent out from the winding-unwindingmachine 107 with an unvulcanized outer rubber layer 13 using a secondextruder 108, and the formed hose body 109 is wound by a winding machine110. In the present embodiment, a vulcanized hose 112 obtained by avulcanization step performed by a vulcanization device 111 is wound bythe winding machine 110 after the hose body 109 is sent out from thesecond extruder 108 but before wound by the winding machine 110;however, the vulcanization step can be performed after the hose body 109is wound by the winding machine 110. Furthermore, before and after thevulcanization device 111, a wrapping device 113 and an unwrapping device114 are provided in order to wrap or unwrap a protective cloth such as anylon cloth around the hose body 109. Note that, in FIG. 2, after thevulcanization, the unvulcanized hose 115 on which a nylon cloth iswrapped by the wrapping device 113 becomes a hose 116 that is in a statebefore unwrapping the nylon cloth. The vulcanization step will bedescribed below.

Next, in the step S104, a hydraulic hose 118 is completed by removingthe mandrel 101, using a mandrel removing device 117, from the hose 116that is sent out from the winding machine 110 and unwrapped after thevulcanization.

<Vulcanization Step>

As illustrated in FIG. 3, by the wrapping device 113, a nylon cloth 119is wrapped around the hose body 109 sent out from the second extruder108. The hose body 109 covered with the nylon cloth 119 is thentransferred into the vulcanization device 111. The vulcanization device111 is a continuous vulcanization device with hot-air circulation thatallows the vulcanization to proceed by hot wind 120. The vulcanizationmethod is an oven vulcanization method.

FIG. 4 is a partially cross-sectional view explaining an example of alayer structure around a mandrel 101 inserted into a vulcanizationdevice. As illustrated in FIG. 4, the inner rubber layer 11 is formedaround the mandrel 101, the reinforcing layer 12 is further formedtherearound, and the outer rubber layer 13 is further formedtherearound. The nylon cloth 119 is wrapped around the outer rubberlayer 13, and the outer rubber layer 13 is heated in this condition toproceed the vulcanization step.

As described above, the vulcanization temperature is preferably from130° C. to 180° C., and the vulcanization time (that is, thevulcanization time in the vulcanization device 111) is preferably from30 minutes to 240 minutes. Using this temperature range and thevulcanization time, a hydraulic hose having excellent adhesion betweenthe inner rubber layer 11 and the reinforcing layer 12 and between theouter rubber layer 13 and the reinforcing layer 12 is obtained. Here, ahydraulic hose having excellent adhesion between an inner rubber layer11 and/or an outer rubber layer 13 and a metal reinforcing layer 12 canbe produced by forming the inner rubber layer 11 and/or the outer rubberlayer 13 using the rubber composition according to the embodimentdescribed above.

Note that, according to the rubber composition, since a suitable watercontent can be stably maintained in the composition until immediatelybefore the vulcanization, adhesion failure and decrease in adhesion dueto insufficient water content can be suppressed even when an ovenvulcanization method that causes great amount of water evaporation isused. The rubber composition according to the embodiment can be,needless to say, suitably used in a production of rubber products usingconventionally known another vulcanization method. Examples of anothervulcanization method include press vulcanization, steam vulcanization,hot water vulcanization, and the like.

Furthermore, in the embodiment described above, production steps ofcontinuous treatment are exemplified; however, the vulcanized rubberproducts can be also produced by a method in which the rubber layer andthe reinforcing layer are produced in separate steps and then adhered.

The hydraulic hose produced by the production method according to thepresent embodiment can be used in various applications. The hydraulichose can be suitably used as, for example, air conditioner hose forvehicles, power steering hose, hydraulic hose for hydraulic systems ofconstruction vehicles, and the like.

Furthermore, in the present embodiment, a hydraulic hose as a laminatedbody of the rubber composition and a metal and as a vulcanized rubberproduct has been explained; however, the present technology is notlimited to this, and for example, the present technology can also beused in other rubber laminated bodies such as a conveyer belt.

As described above, according to the method of producing a laminatedbody of the rubber composition and a metal, vulcanized rubber product,and vulcanized rubber product, vulcanized rubber products havingexcellent adhesion between a rubber layer and a reinforcing layer can beprovided even when a continuous production method with an ovenvulcanization method is used. In particular, a composition that can forma rubber product having excellent adhesion toward a reinforcing layercan be provided even in the case where the composition is stored in adried state for a long period of time. This vulcanized rubber productcan be suitably used in hydraulic hose, high pressure hose, and thelike.

EXAMPLES

The present technology will be described in further detail withreference to the examples performed in order to clearly show the effectof the present technology. Note that the present technology is notlimited by the working examples and comparative examples describedbelow.

<1. Production of Rubber Composition>

Working Example 1

In 100 parts by mass of a diene polymer containing 50 mass % of achloroprene rubber (trade name: Denka Chloroprene S-41, manufactured byDenki Kagaku Kogyo K. K; mercaptan-modified chloroprene rubber; Mooneyviscosity (ML1+4, 125° C.): 47) and 50 mass % of styrene butadienerubber (trade name: Nipol 1502, manufactured by Zeon Corporation;emulsion polymerization SBR; bonding styrene content: 23.5 mass %;Mooney viscosity (ML1+4, 100° C.): 52), 0.8 parts by mass of sulfur(manufactured by Hosoi Chemical Industry Co., Ltd.), 0.5 parts by massof a thiuram vulcanization accelerator (tetramethylthiuram monosulfide;trade name: Sanceler TS-G, manufactured by Sanshin Chemical IndustryCo., Ltd.), 0.5 parts by mass of a guanidine vulcanization accelerator(diphenylguanidine; trade name: Soxinol D-G, manufactured by SumitomoChemical Co., Ltd.), 0.5 parts by mass of a sulfenamide vulcanizationaccelerator (N-t-butylbenzothiazole-2-sulfenamide; trade name: NOCCELERNS-P, manufactured by Ouchi Shinko Chemical Industrial Co., Ltd.), 0.75parts by mass of a thiourea vulcanization accelerator(2-mercaptoimidazoline; trade name: Sanmix 22-80E, manufactured bySanshin Chemical Industry Co., Ltd.), 75 parts by mass of FEF gradecarbon black (trade name: HTC#100, manufactured by NSCC Carbon Co.,Ltd.), 5 parts by mass of type III zinc oxide (manufactured by SeidoChemical Industry Co., Ltd.), 2 parts by mass of magnesium oxide (tradename: Kyowa Mag 150, manufactured by Kyowa Chemical Industry Co., Ltd.),2 parts by mass of stearic acid (manufactured by NOF Corporation), 2parts by mass of an antiozonant (trade name: Ozonone 6C, manufactured bySeiko Chemical Co., Ltd.), and 25 parts by mass of an aroma oil (tradename: A-OMIX, manufactured by Sankyo Yuka Kogyo K. K.) were compoundedand kneaded using a Banbury mixer to produce a rubber composition. Theadhesion and heat resistance of the produced rubber composition wasevaluated. Compounded amount of each of the components are shown inTable 1 below and evaluation results are shown in Table 3 below.

Working Example 2

A rubber composition was produced in the same manner as in WorkingExample 1 except for changing the compounded amount of sulfur to 0.5parts by mass, and the rubber composition was evaluated. Compoundedamount of each of the components are shown in Table 1 below andevaluation results are shown in Table 3 below.

Working Example 3

A rubber composition was produced in the same manner as in WorkingExample 1 except for changing the compounded amount of sulfur to 1.5parts by mass, and the rubber composition was evaluated. Compoundedamount of each of the components are shown in Table 1 below andevaluation results are shown in Table 3 below.

Working Example 4

A rubber composition was produced in the same manner as in WorkingExample 1 except for changing the compounded amount of the thiuramvulcanization accelerator to 0.2 parts by mass, and the rubbercomposition was evaluated. Compounded amount of each of the componentsare shown in Table 1 below and evaluation results are shown in Table 3below.

Working Example 5

A rubber composition was produced in the same manner as in WorkingExample 1 except for changing the compounded amount of the thiuramvulcanization accelerator to 0.6 parts by mass, and the rubbercomposition was evaluated. Compounded amount of each of the componentsare shown in Table 1 below and evaluation results are shown in Table 3below.

Working Example 6

A rubber composition was produced in the same manner as in WorkingExample 1 except for changing the compounded amount of the sulfenamidevulcanization accelerator to 0.8 parts by mass and the compounded amountof the thiourea vulcanization accelerator to 0.6 parts by mass, and therubber composition was evaluated. Compounded amount of each of thecomponents are shown in Table 1 below and evaluation results are shownin Table 3 below.

Comparative Example 1

A rubber composition was produced in the same manner as in WorkingExample 1 except for changing each of the compounded amounts of thethiuram vulcanization accelerator and the guanidine vulcanizationaccelerator to 0.8 parts by mass and compounding no sulfenamidevulcanization accelerator and no thiourea vulcanization accelerator, andthe rubber composition was evaluated. Compounded amount of each of thecomponents are shown in Table 2 below and evaluation results are shownin Table 4 below.

Comparative Example 2

A rubber composition was produced in the same manner as in WorkingExample 1 except for changing each of the compounded amounts of thethiuram vulcanization accelerator and the guanidine vulcanizationaccelerator to 0.4 parts by mass and compounding no sulfenamidevulcanization accelerator and no thiourea vulcanization accelerator, andthe rubber composition was evaluated. Compounded amount of each of thecomponents are shown in Table 2 below and evaluation results are shownin Table 4 below.

Comparative Example 3

A rubber composition was produced in the same manner as in WorkingExample 1 except for changing the compounded amount of the thiuramvulcanization accelerator to 0.4 parts by mass and compounding noguanidine vulcanization accelerator and no thiourea vulcanizationaccelerator, and the rubber composition was evaluated. Compounded amountof each of the components are shown in Table 2 below and evaluationresults are shown in Table 4 below.

Comparative Example 4

A rubber composition was produced in the same manner as in WorkingExample 1 except for compounding no thiourea vulcanization accelerator,and the rubber composition was evaluated. Compounded amount of each ofthe components are shown in Table 2 below and evaluation results areshown in Table 4 below.

Comparative Example 5

A rubber composition was produced in the same manner as in WorkingExample 1 except for compounding no sulfenamide vulcanizationaccelerator, and the rubber composition was evaluated. Compounded amountof each of the components are shown in Table 2 below and evaluationresults are shown in Table 4 below.

Comparative Example 6

A rubber composition was produced in the same manner as in WorkingExample 1 except for changing the compounded amount of sulfur to 1.6parts by mass, and the rubber composition was evaluated. Compoundedamount of each of the components are shown in Table 2 below andevaluation results are shown in Table 4 below.

Comparative Example 7

A rubber composition was produced in the same manner as in WorkingExample 1 except for changing the compounded amount of the thiuramvulcanization accelerator to 0.1 parts by mass, and the rubbercomposition was evaluated. Compounded amount of each of the componentsare shown in Table 2 below and evaluation results are shown in Table 4below.

Comparative Example 8

A rubber composition was produced in the same manner as in WorkingExample 1 except for changing the compounded amount of the thiuramvulcanization accelerator to 0.8 parts by mass, and the rubbercomposition was evaluated. Compounded amount of each of the componentsare shown in Table 2 below and evaluation results are shown in Table 4below.

Comparative Example 9

A rubber composition was produced in the same manner as in WorkingExample 1 except for changing the compounded amount of the thiuramvulcanization accelerator to 0.6 parts by mass, the compounded amount ofthe guanidine vulcanization accelerator to 0.1 parts by mass, and thecompounded amount of the thiourea vulcanization accelerator to 0.6 partsby mass, and the rubber composition was evaluated. Compounded amount ofeach of the components are shown in Table 2 below and evaluation resultsare shown in Table 4 below.

Comparative Example 10

A rubber composition was produced in the same manner as in ComparativeExample 9 except for changing the compounded amount of the guanidinevulcanization accelerator to 0.75 parts by mass, and the rubbercomposition was evaluated. Compounded amount of each of the componentsare shown in Table 2 below and evaluation results are shown in Table 4below.

Comparative Example 11

A rubber composition was produced in the same manner as in WorkingExample 1 except for changing the compounded amount of sulfur to 0.6parts by mass, the compounded amount of the sulfenamide vulcanizationaccelerator to 0.1 parts by mass, and the compounded amount of thethiourea vulcanization accelerator to 0.6 parts by mass, and the rubbercomposition was evaluated. Compounded amount of each of the componentsare shown in Table 2 below and evaluation results are shown in Table 4below.

Comparative Example 12

A rubber composition was produced in the same manner as in ComparativeExample 11 except for changing the compounded amount of the sulfenamidevulcanization accelerator to 1.0 parts by mass, and the rubbercomposition was evaluated. Compounded amount of each of the componentsare shown in Table 2 below and evaluation results are shown in Table 4below.

Comparative Example 13

A rubber composition was produced in the same manner as in WorkingExample 1 except for changing the compounded amount of the thioureavulcanization accelerator to 1.6 parts by mass, and the rubbercomposition was evaluated. Compounded amount of each of the componentsare shown in Table 2 below and evaluation results are shown in Table 4below.

TABLE 1 Working examples 1 2 3 4 5 6 CR 50 50 50 50 50 50 SBR 50 50 5050 50 50 Sulfur 0.8 0.5 1.5 0.8 0.8 0.6 Vulcanization 0.5 0.5 0.5 0.20.6 0.5 accelerator A Vulcanization 0.5 0.3 0.5 0.6 0.5 0.5 acceleratorB Vulcanization 0.5 0.5 0.5 0.5 0.5 0.8 accelerator C Vulcanization 0.750.75 0.75 0.75 0.75 0.6 accelerator D Carbon black 75 75 75 75 75 75Zinc oxide 5 5 5 5 5 5 Magnesium 2 2 2 2 2 2 oxide Stearic acid 2 2 2 22 2 Antiozonant 2 2 2 2 2 2 Process oil 25 25 25 25 25 25

TABLE 2 Comparative examples 1 2 3 4 5 6 7 8 9 10 11 12 13 CR 50 50 5050 50 50 50 50 50 50 50 50 50 SBR 50 50 50 50 50 50 50 50 50 50 50 50 50Sulfur 0.8 0.8 0.8 0.8 0.8 1.6 0.8 0.8 0.8 0.8 0.6 0.6 0.8 Vulcanization0.8 0.4 0.4 0.5 0.5 0.5 0.1 0.8 0.6 0.6 0.5 0.5 0.5 accelerator AVulcanization 0.8 0.4 0.5 0.5 0.5 0.5 0.5 0.1 0.75 0.5 0.5 0.5accelerator B Vulcanization 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.1 1 0.5accelerator C Vulcanization 0.75 0.75 0.75 0.75 0.6 0.6 0.6 0.6 1.6accelerator D Carbon black 75 75 75 75 75 75 75 75 75 75 75 75 75 Zincoxide 5 5 5 5 5 5 5 5 5 5 5 5 5 Magnesium 2 2 2 2 2 2 2 2 2 2 2 2 2oxide Stearic acid 2 2 2 2 2 2 2 2 2 2 2 2 2 Antiozonant 2 2 2 2 2 2 2 22 2 2 2 2 Process oil 25 25 25 25 25 25 25 25 25 25 25 25 25

Details of each of the components listed in Tables 1 and 2 are asdescribed below.

-   CR: trade name: Denka Chloroprene S-41, manufactured by Denki Kagaku    Kogyo K.K; non-sulfur-modified chloroprene rubber; Mooney viscosity    (ML1+4, 125° C.): 47-   SBR: trade name: Nipol 1502, manufactured by Zeon Corporation;    emulsion polymerization SBR; bonding styrene content: 23.5 mass %;    Mooney viscosity (ML1+4, 100° C.): 52-   Sulfur: manufactured by Hosoi Chemical Industry Co., Ltd.-   Vulcanization accelerator A: tetramethylthiuram monosulfide; trade    name: Sanceler TS-G, manufactured by Sanshin Chemical Industry Co.,    Ltd.-   Vulcanization accelerator B: N,N′-diphenylguanidine; trade name:    Soxinol D-G, manufactured by Sumitomo Chemical Co., Ltd.-   Vulcanization accelerator C: N-t-butyl-2-benzothiazolyl sulfenamide;    trade name: NOCCELER NS-P, manufactured by Ouchi Shinko Chemical    Industrial Co., Ltd.-   Vulcanization accelerator D: 2-mercaptoimidazoline; trade name:    Sanmix 22-80E, manufactured by Sanshin Chemical Industry Co., Ltd.    (Note that, in the working examples and comparative examples, the    vulcanization accelerator D was compounded based on the net content    (100 mass %) of 2-mercaptoimidazoline contained in the commercially    available Sanmix 22-80E and was not compounded based on the mass of    the commercially available Sanmix 22-80E in which the purity of the    2-mercaptoimidazoline is 80 mass %)-   Carbon black: FEF grade carbon black (trade name: HTC#100,    manufactured by NSCC Carbon Co., Ltd.)-   Zinc oxide: type III zinc oxide (manufactured by Seido Chemical    Industry Ltd.)-   Magnesium oxide: trade name: Kyowa Mag 150, manufactured by Kyowa    Chemical Industry Co., Ltd.-   Stearic acid: manufactured by NOF Corporation-   Antiozonant: trade name: Ozonone 6C, manufactured by Seiko Chemical    Co., Ltd.-   Process oil: aroma oil; trade name: A-OMIX, manufactured by Sankyo    Yuka Kogyo K. K.    <Adhesion Test>

An unvulcanized rubber sheet having a square shape (width 120 mm×length120 mm×thickness 2 mm) was produced by kneading a rubber compositionhaving a composition shown in Table 1 by a conventional method. Theadhesion between the obtained unvulcanized rubber sheet and thebrass-plated wire was evaluated under the following conditions.

(Adhesion Evaluation 1: Initial Adhesion and Wire Peeling Test)

On the surface of the produced unvulcanized rubber sheet, three sets ofa set of five brass-plated wires (diameter: 0.6 mm; length: 100 mm) thatwere put side by side were arranged, and the both ends thereof wereadhered and fixed by a tape. Then, the fixed unvulcanized rubber sheetwas vulcanized at 142° C. for 90 minutes. Thereafter, the wires werepeeled from the rubber sheet, and the surface conditions of the peeledwires were visually observed. The evaluation of adhesion was performedby calculating the proportion of the wires having the rubber attached tothe surface thereof, relative to the total number of sets of the wiresadhered to the unvulcanized rubber sheet. Evaluation criteria are shownbelow.

∘: proportion of the wires having the rubber attached to the surfacethereof was 80% or greater

x: proportion of the wires having the rubber attached to the surfacethereof was less than 80%

(Adhesion Evaluation 2: After Thermal Deterioration)

After the produced unvulcanized rubber sheet was placed in a constanttemperature and high humidity chamber at 50° C. with a relative humidityof 95% RH for 168 hours, the unvulcanized rubber sheet was removed fromthe high humidity chamber. Within 2 hours from the removal, the wireswere peeled from the rubber sheet, and the surface conditions of thepeeled wires were visually observed. Evaluation criteria are shownbelow.

∘: proportion of the wires having the rubber attached to the surfacethereof was 60% or greater

x: proportion of the wires having the rubber attached to the surfacethereof was less than 60%

<Heat Resistance Evaluation>

Heat aging test (100° C.×336 hr) was performed in accordance with JIS K6257:2010 as the heat resistance test. After heating the vulcanizedrubber at a specified temperature for a specified time using a heataging tester, elongation at break (EB) was measured in accordance withJIS K 6251:2010, and hardness (HS) was measured in accordance with JIS K6253-3:2012. The heat resistance was evaluated by examining the agingproperties of the vulcanized rubber by determining the rate of change inelongation at break (ΔEB) or the rate of change in hardness (ΔHS)relative to the values prior to the heat treatment. Evaluation criteriaare shown below. Test results are shown in Tables 3 and 4 below.

∘: ΔEB was from −40% to 0%, and ΔHS was from 0 to 20

x: a case where the evaluation was not “∘”

TABLE 3 Working examples 1 2 3 4 5 6 Adhesion 90 90 100 90 90 90evaluation 1 Adhesion 90 80 100 90 90 90 evaluation 2 Heat ∘ ∘ ∘ ∘ ∘ ∘resistance evaluation

TABLE 4 Comparative examples 1 2 3 4 5 6 7 8 9 10 11 12 13 Adhesion 9090 90 80 90 100 90 90 90 90 90 40 50 evaluation 1 Adhesion 50 90 50 5090 100 90 50 90 40 90 40 50 evaluation 2 Heat ∘ x x ∘ x x x ∘ x ∘ x ∘ ∘resistance evaluation

As shown in Tables 3 and 4, all of the rubber compositions according toWorking Examples 1 to 6 containing a predetermined amount of sulfur, apredetermined amount of a thiuram vulcanization accelerator, apredetermined amount of a guanidine vulcanization accelerator, apredetermined amount of a sulfenamide vulcanization accelerator, and apredetermined amount of a thiourea vulcanization accelerator relative tothe amount of the diene polymer exhibited excellent adhesion and heatresistance. On the other hand, for the cases where at least one type ofa thiuram vulcanization accelerator, guanidine vulcanizationaccelerator, sulfenamide vulcanization accelerator, or thioureavulcanization accelerator was not compounded, at least one of theevaluation result of adhesion or heat resistance was deteriorated(Comparative Examples 1 to 5). It is thought that this is becauseadhesion and heat resistance were not enhanced in a well-balanced mannerdue to not containing the four types of the vulcanization accelerators.Furthermore, also for the cases where the compounded amount of at leastone type of sulfur, a thiuram vulcanization accelerator, guanidinevulcanization accelerator, sulfenamide vulcanization accelerator, orthiourea vulcanization accelerator was outside the range of thespecified amount, at least one of the evaluation result of adhesion orheat resistance was deteriorated (Comparative Examples 6 to 13). It isthought that this is because adhesion and heat resistance were notenhanced in a well-balanced manner as a result of not achievingsufficient crosslinking characteristics due to losing the balance of thesulfur and the four types of the vulcanization accelerators.

The invention claimed is:
 1. A rubber composition comprising: from 0.5parts by mass to 1.5 parts by mass of sulfur, from 0.2 parts by mass to0.6 parts by mass of a thiuram vulcanization accelerator, from 0.2 partsby mass to 0.6 parts by mass of a guanidine vulcanization accelerator,from 0.15 parts by mass to 0.8 parts by mass of a sulfenamidevulcanization accelerator, and from 0.1 parts by mass to 1.5 parts bymass of a thiourea vulcanization accelerator, per 100 parts by mass of adiene polymer containing a chloroprene rubber and a styrene butadienerubber, wherein, in the diene polymer, a content of the chloroprenerubber is not less than 40 mass %, and a content of the styrenebutadiene rubber is not greater 60 mass %.
 2. A vulcanized rubberproduct comprising the rubber composition described in claim
 1. 3. Therubber composition according to claim 1, wherein, the compounded amountof the diene polymer is from 20 mass % to 70 mass % relative to thetotal amount of the rubber composition.